The aspect of spreader construction with which the present invention is essentially concerned is that of causing minor rotation of the cargo container about a vertical axis with respect to the crane which supports the spreader. Regarding spreaders which are operated in pendant relation with a crane, the principal arrangement found in the prior art is one in which the spreader comprises two horizontal frames arranged one over the other and connected to each other on a central horizontal pivot joint by expensive massive bearing structure. While this arrangement permits large angular ranges of skewing of the cargo container, e.g., up to 90.degree. relative movement between the two horizontal frames, the present invention recognizes that 15.degree. or 20.degree. of skewing movement is adequate for a vast number of operating environments. With the concept in mind that the small skewing range might be practical, the possibility of building a spreader in accordance with a fundamentally different design has been a paramount motivation of this invention.
The most important object of the invention is to achieve a lower cost design in cargo container spreaders of a type having moderate skewing capability than has been heretofore available to the shipping industry.
Another object is to provide skewable spreaders of compact design.
Still another object is to construct a skewable spreader including self leveling structure with the result that the combination of skewing and tilting capabilities enables the spreader to undergo substantially universal adjustment within the tilting and skewing ranges of the spreader.